Graphics display system and method

ABSTRACT

A system for displaying on a standard television monitor a horizontal line along a scan line or a vertical line orthogonal to the scan line wherein coded digital signals from a memory define the location of the starting point of the line and also identify the line as either a horizontal or a vertical line. For horizontal line drawing, circuit means are provided to respond to the starting point identification to gate the beam on and to the horizontal line identification to maintain the beam gated on along a scan line until the end of the line. For vertical line drawing, the beam is gated on at the starting point and a recirculating shift register stores the starting point identification to gate the beam on at the corresponding positions in successive scan lines.

United States Patent [191 Levine June 28, 1974 GRAPHICS DISPLAY SYSTEMAND METHOD Inventor: Michael Robert Levine, Ann Arbor,

Mich.

Assignee: Ann Arbor Terminals, lnc., Ann

Arbor, Mich.

Filed: July 23, 1973 Appl. No.: 381,577

Related US. Application Data Continuation of Ser. No. 150,288, June 7,abandoned.

US. Cl.... 340/324 AD, l78/DlG. 3, 340/1725 Int. Cl. G06f 3/14 Field ofSearch 340/324 A, 324 AD;

l78/DIG. 3, 6.8, 7.5 D

[5 6] References Cited UNITED STATES PATENTS 10/1963 Kronenberg et a1.340/324 AD 9/1968 Lee 340/324 AD 10/1969 Manber 340/324 AD 6/1971 Kraatz.[340/324 AD 3,646,257 2/1972 Epstein et a1. l78/DlG. 3 3,668,687 6/1972Hale 340/324 AD 3,713,135 1/1973 Lazecki 340/324 AD PrimaryExaminerDavid L. Trafton Attorney, Agent, or FirmBarnes, Kisselle,Raisch & Choate [5 7] ABSTRACT ing, circuit means are provided torespond to the starting point identification to gate the beam on and tothe horizontal line identification to maintain the beamgated on along ascan line until the end of the line. For vertical line drawing, the beamis gated on at the starting point and a recirculating shift registerstores the starting point identification to gate the beam on at thecorresponding positions in successive scan lines.

19 Claims, 5 Drawing Figures ,2 Y 52 raster vert sync.

oriz. stable sync. L MV 4 L 12 so mam memory 3; standard dotoddresstelevision monitor 66 address or can 69 0 cntr 2 J6 inputl load j reg.control and bt- 19 T /l 49 MV computer Pland and recirculating shiftregister f and memory I i ,L l

1 GRAPHICS DISPLAY SYSTEM AND METHOD This is a continuation ofapplication Ser. No. 150,288, filed June 7, 1971 now abandoned.

This invention relates to digital data processing systems and moreparticularly to a graphics display system utilizing a television rasterscan wherein digital data is used to generate a graphics displayincluding dots and horizontal and vertical lines.

Graphics display systems presently commercially available fall generallyinto three categories. The first type is a so-called limited graphicsdisplay wherein one point is displayed during each scan line in responseto an instruction from memory. So long as the change in the functionbeing displayed is small from scan line to scan line, the technique iseffective because the eye will integrate the dots as a continuous linefunction. However, as the change in the function increases from scanline to scan line, the eye does not effectively integrate the function.This causes the function to lose continuity to the viewer and, in anextreme case of large differences, the display becomes meaningless.Hence although a limited graphics system can display a slowly varyingfunction, it cannot effectively display rapidly varying functions. Thesecond type, commonly known as a full graphics display, is implementedby providing one memory location for every possible dot position on thedisplay. Lines are drawn by displaying each dot in response to aseparate digital instruction. Hence a line consisting of three dotsrequires three separate instructions from memory. Although the fullgraphicssystem can effectively display rapidly varying functions, itrequires a large memory that is too expensive for many applications. Thethird type which may be termed character graphics has a limitedcharacter set, typically 64 characters; and the display field is dividedinto contiguous character cells, as contrasted to the dot matrix of afull graphics system. A designated character may be displayed at adesignated cell. A graphic display is gen erated by selectingappropriate characters for contiguous cells. However, resolution with acharacter graphics display can be no greater than the cell size,typically one percent of the full graphics resolution capability.Character graphics, like limited graphics, cannot effectively display arapidly varying function.

An object of the present invention is to provide a graphics displaysystem and method that overcome the aforementioned disadvantages of theaforementioned displays.

Further objects of the present invention are to provide a graphicsdisplay system and method that provide effective display of rapidlyvarying functions and that reduce the number of memory locationsrequired, and hence are low in cost, by comparison to prior art capableof displaying rapidly varying functions.

Other objects, features and advantages of the present invention willbecome more apparent in connection with the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a block diagram illustrating a first embodiment of thegraphics display system of the present invention;

FIG. 2 is a coding format of the digital code data for the embodiment ofFIG. 1;

FIG. 3a is a simplified display illustrating the generation ofhorizontal andvertical lines by means of the circuit of FIG. l;

FIG. 3b is a table of coding for generating the display of FIG. 3a withthe circuit of FIG. 1;

FIG. 4 is a block diagram illustrating a second embodiment of a displaysystem of the present invention; and

FIG. 5 is a coding format for the system of FIG. 4.

Referring in greater detail to the drawings, digitally coded data from acomputer 10 is loaded into a main memory 12 via an input register 14under control of a load control circuit 18 which also controls anaddress counter 16. In response to a strobe command at line 19 from thecomputer 10, the data necessary to generate a complete display frame ona standard television monitor 20 is entered into memory 12. It will beunderstood that the particular manner in which data is loaded intomemory 12 is not an essential feature of the present invention. Variousdifferent techniques can be used. For

purposes of illustration, memory 12 is a random access memory, forexample, the memory known commercially as MOS RAM, that is loadedsequentially and then read sequentially under the control of the addresscounter 16 to generate a display on monitor 20.

By way of further illustration, one typical display contains, forexample, 256 scan lines each of which has 512 dot positions at which adot could be displayed. For reasons that will later be apparent, eachbyte or digital word from computer 10 has the format shown in FIG. 2wherein nine of the bits 22 (FIG. 2) is a number specifying one of the512 dot positions on a scan line. For reasons as will later be describedin greater detail, the nine-bit dot position specified by the data inmemory 12 identifies the number of dot positions to the next dot to bedisplayed. The remaining three bits are a line feed bit 24, a horizontalline drawing bit 26 and a vertical line drawing bit 28.

The nine bits 22 in each byte are transferred sequentially from memory12 under the control of the address counter 16 to a countdown counter30. For the above example, counter 30 has nine stages so that it cancount up to 512. Simultaneously the line feed bit 24 is fed through abistable multivibrator 32 to an AND gate 34. The horizontal line drawingbit 26 is steered into a pair of AND gates 36, 38 in a horizontal linegenerator 40 designated by broken lines; and the vertical line drawingbit 28 is steered to a pair of AND gates 42, 44 in a vertical linegenerator 46 designated by broken lines.

A raster scan timing cicuit 50 generates timing signals applied,respectively, via line 52 to counter 16, via line 54 to gate 34, and vialine 56 to multivibrator 32. The timing signal applied to gate 34 vialine 54 is a dot clock pulse train containing the desired number ofpulses, 512 pulses for the above example, to determine the number of dotpositions which can be illuminated along each horizontal scan line atmonitor 20. Hence timing circuit 50 provides a burst of 512 pulses insynchronism'with the beam as it traces each horizontal scan line. Thedot clock pulse train is applied to gate 34 only during the usefulportion of a horizontal scan on the display; that is, the clock is notapplied at gate 34 during horizontal and vertical retrace of the beam.The timing signal applied to counter 16 via line 52 is the vertical syncpulse which is also fed to a mixer 60 to synchronize the display frameat monitor 20 with the readout at memory 12. The timing signal formultivibrator 32 on line 56 is the horizontal sync pulse which is alsoapplied to mixer 60 to synchronize. the scan lines 3 1 to memoryreadout. Multivibrator 32 is set by a binary ONE in the line feed bit 24to disable gate 34.The next horizontal sync pulse at line 56 resetsmultivibrator 32, enabling gate 34 to pass the dot clock pulse train tocounter 30.

The pulses passed to counter 30 by gate 34 count down the number storedin the counter 30 from memory 12. As the counter 30 passes through zero,an output pulse, commonly known as the underflow pulse, is generated bycounter 30 and applied to line 31. The underflow pulse on line.31 isapplied to the other inputs of all four AND gates 36, 38, 42, 44. Theunderflow pulse on line 31 is'also fed to an OR gate 64, an OR gate 65inthe input of the address counter 16, and via an OR gate 67 and a delay66 to the load input 69 of the counter 30. Gate 67 also receives avertical sync pulse on line 52 to initially load counter 30 at the startof a display frame. The underflow pulse on line 31 passes directlythrough gate 64 and-an AND gate 71- to mixer 60 to intensify the beam atmonitor 20. Gate-71 is controlled by a blanking signal from circuit 50which disables gate 71 to prevent video signals from reaching mixer 60during horizontal and vertical retrace periods and at the last dotposition on each scan line, i.e., dot position 512 for the aboveexample. The underflow pulse fed to counter 16 via the gate 65increments the address counter 16 so that the next digital word isavailable for entry into counter 30. The underflow pulse applied to theload input 70 via' gate 67 and delay 66 causes the next word to beentered into counter 30. The. slight delay introduced at 66 assures thatthe new word is loaded in counter 30.

A ONE in the horizontal line drawing bit 26 (designating that ahorizontal line is to be drawn) steersan underflow pulse through gate 36to set a bistable multivibrator 68 to its set condition. In its setcondition, multivibrator 68 provides a video signal -to mixer 60 viagates 64 and 71 to-intensify the beam at monitor 20 until multivibrator68 is reset. A ZERO in bit 26 will steer an underflow pulse on line 31through gate 38 to reset multivibrator 68 and terminate the horizontalline. A ONE in the vertical line drawing 28 (designating that a verticalline is to be drawn) will steer an underflow pulse through gate 42causing the underflow pulse to be stored in a recirculating shiftregister memory 70. The recirculating memory 70 has a number of stagescorresponding to the number of effective dot positions on the display,i.e., 512 dot positions for the above example. Thedotclock pulse trainfrom timing circuit 50 is also applied to memory 70 via line 54 to shiftthe register 70, causing each stored pulse to circulate in synchronismwith the beam at monitor 20. Since pulses are entered in memory 70 bythe underflow pulse, the stored pulse will provide avideo pulse to mixer60 via gates '64 and 71 at the same dot position during subsequent scanlines to cause a vertical line to be displayed. A ZERO in bit 28 willsteer an underflow pulse on line 31 through gate 44 to clear memory 70at that dot position and terminate the vertical line. Hence thecomposite video developed by mixer 60 contains horizontal and verticalsync pulses from the raster scan timing circuit 50 to synchronize thedisplay frame with memory 12 together with digital video signals formedby the underflow pulse on line 31 and the'outputs from the horizontalline generator 40 and the vertical line generator 46. i

The construction and operation of the data display system describedhereinabove in connection with FIG. 1 will be more clearly understood byreference to the exemplary display shown in FIG. 3a and the'corresponding digital codes shown in the table of FIG. 312. To generatethe display shown in FIG. 3a, the 15 words shown in the table are storedin memory 12 at sequential memory addresses 0-14 (Column 1 of thetable). At the beginning of the frame designated by point 0 at the lefthand of the first upper scan line (FIG. 3a), the data from memory.address 0 0 is loaded in counter 30. The corresponding line feed bit 24is fed to multivibrator 32 and horizontal and vertical line drawing bits26, 28 are fed to the horizontal and vertical line generators 40, 46. Inresponse to the ONE'in the line feed bit 24, gate 34 is disabled toinhibit transfer of a dot clock pulse train to counter 30 until theoccurrence of the horizontal sync pulse at the end of the first scanline. When the beam reaches the end of the first scan line,multivibrator 32 is reset to enable gate 34 and begin countdown atcounter 30. For the example being described, because the dot address 128was entered in counter 30, upon the occurrence of the 128th dot clockpulse," an underflow pulse is generated by counter 30 and transferredvia gates '64 and 71 and mixer 60 to the monitor 20 to generate a dot atthe first display point 1 designated in FIG. 3d. Simultaneously, the ONEin the horizontal line bit 26 steers the underflow pulse through gate 36to set multivibrator 68 which in turn generates a digital signal tomaintain the beam on at the monitor 20. At the same time, the ONE in thevertical line bit 28 steers the underflow pulse through gate 42 andenters it into memory 70 to start the vertical line from point 1. Theunderflow pulse also increments the address counter 16 and, after ashort delay, loads the contents of memory address 1 into counter 30. Itis noted that the digital code at memory address 1 contains the number256 which represents the distance in dot positions to the next dot to bedisplayed at point 2 (FIG. 3a).

Since theline feed bit 24 is a ZERO; multivibrator 32 remains in itsreset state so that the gate 34 remains enabled and the dot clock pulsetrain at line 54continues to be passed via gate 34 to counter 30 tocount down the dot address 256. After 256 pulses are counted, a secondunderflow pulse is generated by counter 30 at the dot position 2 (FIG.3a). The second underflow pulse is steered by the ZERO in the horizontalline bit 26 through gate 38 to reset multivibrator 68, thereby turningoff the beam at the number 2" dot position. The second underflow pulseis also steered by the ONE in the vertical line bit 28 through gate 42into memory 70 to start the vertical line from point 2. The secondunderflow pulse increments the address counter and loads the contents ofmemory address 2 into counter 30. Because the line feed bit 24 is a ONE,multivibrator 32 is set to inhibit transfer of the dot clock pulse trainto the counter 30, and the beam remains off from the number 2 dotposition to the end of the second scan line. At the end of the secondscan line, the horizontal sync pulse resets multivibrator 32 to enablegate 34 to pass the dot clock pulse train to counter 30.

When the beam reaches the 128th dot position in the third scan line, adigital video signal is generated by memory 70 to display a dot invertical'alignment with the dot position 1*. When the beam reaches the384th dot position, a second video. signal is generated by memory 70 todisplay a dot in the third scan line in vertical alignment with dotposition 2. When the beam reaches the 512th dot position, point 3 (FIG.3a), counter 30 generates a third underflow pulse toincre: ment theaddress counter and load the contents of memory address 3 into counter30. The underflow pulse is blanked at the AND gate 71. From theforegoing partial description, the manner in which the remainder of thedisplay is generated will be apparent.

Several important features of the data format to generate both verticaland horizontal lines merit special attention. Memory 12 contains only adot address corresponding to the number of dot positions to the next dotto be displayed within the scan line. The line feed bit 24 determineswhether the dot is to be displayed at the dot address number in the linebeing scanned or in the next succeeding line. In response to a ZERO linefeed bit 24, a dot will be displayed in the line being scanned; and inresponse to a ONE, the dot will be displayed in the next succeedingline. Where several scan lines are to be traversed without generating adisplay, except for the dots, if any, generated by memory 70, thesuccessive dot addresses will be the number 512 coupled with a ONE inline feed bit 24. The horizontal line bit 26 determines whether ahorizontal line. is to be started or stopped at the dot addressspecified. The vertical line bit 28 determines whether a vertical lineis to be started or stopped.

One of the more significant features of the present invention is thatthe display is generated with only a small memory. For example, based onthe display of FIG. 3a, only words (or 180 bits) of memory wererequired. An equivalent display generated by a prior art system of thefull graphics type would have required 6,144 bits of memory because abit must be stored for every possible dot position within the dot field.The drastic reduction in memory required is due to three factors. Thedigital code is a number specifying where the dot is to be positionedwithin possible dot positions in the dot matrix of the display. Hencememory 12 is only required to store the number of dots to be displaedrather than the total number of dot positions that are required with afull graphics system of the prior art. Thus a significant advantage isachieved in a display composed only of dots. However, still furtherreductions are achieved because horizontal and vertical lines can bedrawn by storing only two words.

Referring to the alternative embodiment illustrated in FIG. 4, sincemany of the circuit components function in substantially the same manneras those previously described in connection with FIG. 1, similarcomponents are designated by a prime numeral. Digital data is enteredinto a main memory 12' from a computer 10' via an input register 14 anda load control 18'. For a display of the type described in connectionwith FIG. 1, each digital word may again consist of nine dot addressbits 90 (FIG. 5), a line feed bit 92, a horizontal line bit 94 and avertical line bit 96. Although the overall format of the code in F IG. 5corresponds to that described in connection with FIG. 2, the numberdesignated by the nine bit dot address 90 is the absolute dot positionin a scan-line as contrasted to the distance to the next dot to bedisplayed (dot address 22, FIG. 2). During a display, each word is readsequentially from memory 12 under the control of counter 16'. Thehorizontal and vertical line bits 94, 96 perform the same functiondescribed in connection with FIG. 1 to condition the AND gates 36, 38",42', 44. The nine-bit dot address 90 is applied to one input of acomparator 100. In the embodiment of FIG. 4, the dot clock pulse trainon line 54' is applied to a count-up counter 102 capa-' ble of countingup the total number of useable dot positions on each scan line. For theexample described in connection with FIG. 1, counter 102 is a nine-stagecounter to count up to 512 dot positions. Counter 102 also receives aninput reset pulse from the vertical sync line 52 to initiallysynchronize the counter with the beginning of the display frame atmonitor 20. During each scan line at monitor 20, counter l02'receives aburst of 512 dot clock pulses and repeats the count from zero to 511during each scan line. The instantaneous count in counter 102 is appliedto asecond input of comparator 100 for comparison against the dotposition number from memory 12. Comparator 100 generates an output pulseat line 106 when the instantaneous count at count 102 is equal to thedot position number from memory 12'.

The output of comparator 100 is applied to an AND gate 108 which alsoreceives a conditioning signal from the bistable multivibrator 32'.Multivibrator 32' (FIG. 4), as with multivibrator 32 (FIG. 1), is set bya line feed bit 92 and reset by a horizontal sync pulse on line 56'. Inresponse to a ONE in the line feed bit 92, multi' vibrator 32 disablesAND gate 108 to inhibit the transfer of pulses on line 106 to line 31. Ahorizontal sync pulse on line 56 resets multivibrator 32 enabling gate108 to pass pulses on line 106 to line 31'. The pulse on line 31' (FIG.4) corresponds identically in function to the underflow pulse on line 31from counter 30 (FIG. 1). Hence'the output pulse online 31 istransferred through'gates 64, 71' to mixer 60to form the composite videoapplied to .monitor 20 Simultaneously, the pulse on line 31 enablesthose AND gates 36', 38', 42, 44 that were previously conditioned by thehorizontal and vertical line bits 94, 96. The pulse on line 31' alsoincrements the address counter 16.

The construction and operation of the data display system of- FIG. 4will be more readily understood by reference to the description of FIG.1 and to the manner in which the circuit of FIG. 4 generates the displayof FIG. 3a. The data required by the circuit of FIG. 4 corresponds tothe data in the table of FIG. 3b except that the dot address at memoryaddress 1 is 384 rather than 256; the dot address at memory address 4 is320; the dot address at memory address 10 is 320; and the dot address atmemory address 13" is 384. During the first scan line, comparator 100will generate an output at line 106 when the count in counter 102 equalsthe dot address number 128., The output pulse on line 106 is inhibitedbecause the line feed bit 92 is a ONE. At the end of the first scanline, a horizontal sync pulse on line 56 resets multivibrator 32' toenable gate 108. On the second scan line, when counter 102 equals thenumber 128, an output pulse appears on line 106 and is passed via gate108 to line 31 to cause a dot to be displayed on monitor 20 at point 1(FIG. 3a). The pulse on line 31 is steered by the bit 94 through gate36' to set multivibrator 68 and start a horizontal line. Bit 96 alsosteers the output pulse through gate 42' into memory to start a verticalline. The output pulse also causes the contents of memory address 1 tobe applied to comparator 100. Because dot address (FIG. 5) is anabsolute position along a scan line, the dot address at memory address lspecifies the display point 2 (FIG. 3a) as dot position 384 rather thandot. position 256 (FIG. 3b) for the system of FIG. 1. Hence as the beamtraverses the second scan line, a horizontal line is drawn betweenpoints f1 and 2 (F IG. Qa). When the beam reaches point the count incouniei T02 'rEacEeE tlie' number 384 and comparator 100 generatesanother pulse on line 106. This pulse is steered through gate 38 toreset multivibrator 68' and end the horizontal line. The pulse is alsosteered through gate 42' into memory 70' to start the second verticalline. The remainder of the display is'generated in a mannersubstantially the same as that described in connection with the displaysystem of FIG. 1.

Although the main memories 12, 12 have been described as a random accessmemory with readout control by an address counter 16, other types ofmemory and readout controls could be used. For example, memories 12,12', could be one or more MOS dynamic shift registers recirculatinginsynchronism with the display frame so that data is shifted out in theproper sequence. The horizontal line drawing video generated by circuits40, 40' could be gated with various clocks from" timing circuits 50, 50'to display dotted and dashed lines. Additional bits can be added intomemories 1 2, 12 to specify color or different colors for different dotsor lines. To implement of color display, the color data must also betransferred to memories 70, 70 at the starting point of a verticalline-Although the code format has been described as adding additionalbits to each word to control line feed and horizontal and vertical linedrawing, these controls could be stored as separate words that are readsequentially to generate the display. For example, the dot address wordrequired to display a dot at a given dot position could be preceded by acontrol word to start or end either a horizontal or a vertical line asrequired. The control word would condition the gates 36, 38, 42, 44 sothat on the following dot address word the output pulse on line 31 wouldbe steered in the desired manner in generators 40, '46. The presentinvention also contemplates generating a vertical line of given lengthby a digital word identifying the starting point and the number of dotsin successive scan lines required for the given length. At the startingpoint, the length of the line is entered in recirculating memory (70,FIG. 1; 70', FIG. 4)

and the length is decremented once during each successive scan line.

I claim:

1. In a system for displaying graphics on a beam-type display devicethat exhibits a television raster scan line pattern wherein the beamtraverses successive generally parallel scan lines with a plurality ofpredetermined positions along each scan line corresponding to arespective point from which a line may be drawn in a diis to be drawnfrom said first dot position, first circuit means responsive to saidnumber code to generate a beamswitching control signal whenscanning'reaches said first dot position in said one scan line and meansincluding a recirculating memory responsive to said beam switchingcontrol signal and to said line drawing code for producing a pluralityof beam switching sigpulse train.

8 nals during scan lines subsequent to said one scan line, saidrecirculating memory having at leasta number of stages corresponding tothe number of useable dot positions in any given scan line and beingrecirculated in synchronism with said scanning raster.

2. The system set forth inclaim 1 further comprising a raster scantiming circuit providing a dot clock pulse train containing a number ofpulses equal to said useable number of dot positions in each scan lineand wherein said recirculting memory is a recirculating shift registerthat is shifted in response to said dot clock 3. The method ofgenerating a graphics display on a beam-type display device thatexhibits a television raster scan line pattern wherein the beamtraverses successive generally parallel scan lines with a plurality ofdot positions along each scan line corresponding to respective points atwhich the beam may be intensified to display a dot, said display devicehaving a first predetermined maximum number of dot positions at which adot can be displayed, the steps of providing a plurality of storagelocations for digital data corresponding to a second predeterminedmaximum number of dot positions to be intensified in any given display,said second number of dot positions being substantially less than saidfirst number of dot positions, storing in said storage locations aplurality of digital data words coded to identify selected positions atwhich dots are'to be displayed, successively reading each of said wordsfrom said storage location one by one in synchronism with rasterscanning over a plurality of scan lines while intensifying said beam inresponse to each word when said beam reaches each predetermined dotposition, said words being read successively one by one by readinganother code each time said beam reaches that selected dot positionidentified by that code which was last read, and wherein said data wordsare coded to designate whether each dot is to be displayed at a dotposition specified thereby during the scan line then being traversed bysaid beam or during the next succeeding scan line to be traversed bysaid beam, and further comprising the step of inhibiting beamintensification at a dot position in the scan line being traversed'inresponse to a word coded to designate that the dot be displayed at a dotposition in the next scan line 4. The method of generating a graphicsdisplay on a beam-type display device that exhibits a television rasterscan line pattern wherein the beam traverses successive generallyparallel scan lines with a plurality of dot positions along each scanline corresponding to respective points at which the beam may beintensified to display a dot, said display device having a firstpredetermined maximum number of dot positions at which a dot can bedisplayed, the steps of providing a plurality of storage locations fordigital data corresponding to a second predetermined maximum number ofdot positions to be intensified in any given display, said second numberof dot positions being substantially less than said first number of dotpositions, storing in said storage locations a plurality of digital datawords coded to identify selected positions at which dots are to bedisplayed, successively reading each of said words from said storagelocation one by one in synchronism with raster scanning over a pluralityof scan lines while intensifying said beam in response to each word whensaid beam reaches each predetermined dot position, said words being readsuccessively one by one by reading another code each time said beamreaches that selected dot position identified by that code which waslast read, and wherein said method further comprises the steps of codinga first word to designate that a line is to be drawn from a startingpoint dot position designated by said first word, and then, in responseto said line drawing code, intensifying said beam at a dot positionadjacent said starting point dot position.

5. The method set forth in claim 4 wherein a horizontal line is to bedrawn and said first word is coded to designate that a horizontal lineis to be drawn, and wherein said line is drawn by intensifying said beamat said starting point dot position and then, in response to said linedrawing code, maintaining said beam intensified as it is scanned acrosssaid adjacent dot position.

6. The method set forth in claim 5 wherein a second word is coded todesignate an end point dot position of said horizontal line, and saidsecond word is further coded to designate that drawing of saidhorizontal line is to be terminated at said end point dot position, andwherein said method further comprises turning off said beam at said endpoint dot position in response to said further code of said second word.

7. The method set forth in claim 4 wherein a vertical line is to bedrawn and said first word is coded to designate that a vertical line isto be drawn, and wherein said beam is intensified at said adjacent dotposition by storing said starting point dot position in a recirculatingmemory in response to said line drawing code and recalling said storeddot position at the corresponding dot position in the next successivescan line.

8. The method set forth in claim 7 wherein said recirculating memory isa recirculating shift register, said starting point dot position isstored by entering a pulse in said shift register, and said pulse isrecirculated in said shift register in synchronism with beam scanningeach time said beam completes one scan line.

9. A system for displaying graphics including line-like segments on abeam-type display device that exhibits a television raster scan linepattern wherein the beam traverses successive generally parallel scanlines in a first direction and a plurality of predetermined positionsalong each scan line correspond to points at which the beam may beintensified to display a dot, comprising data storage means providing adigitally coded data signal having first data components each of whichdesignates respective dot positions along said scan lines, said datasignal further having second data components associated with respectivefirst data components and designating whether its associated dotposition is contained in a line segment, first circuit means operable insynchronism with raster scanning on said display device and responsiveto said first data components to generate first video components forintensifying said beam at said designated dot positions and secondcircuit means operable in synchronism with raster scanning on saiddisplay device and responsive to both said first and said second datacomponents to generate second video components for intensifying saidbeam at other dot positions such that associated first and second datacomponents cause said beam to be intensified at oneof said predetermineddot positions on a given line segment and at other dot positions on thesame given line segment.

10. The system set forth in claim 9 wherein said first circuit meansgenerates memory sequencing signals in synchronism with said first videocomponents and wherein said system further comprises means responsive tosaid memory sequencing signals to sequentially transfer data from saidstorage means to said first circuit means.

11. The system set forth in claim 10 further comprising raster scantiming means for generating a dot clock pulse train with each of thepulses therein representing a respective dot position along a scan lineand wherein said first circuit means includes counter means and isresponsive to said dot clock pulse train and said first data componentsto generate said first video components when raster scanning reachessaid dot positions designated by said first data components.

12. The system set forth in claim 11 wherein said counter means isresponsive to said pulse train to provide an instantaneous countrepresentingthe dot position of said beam during eachscan line andwherein said first circuit means further comprises comparison meansoperatively coupled to said storage means and to said counter meansandresponsive to said instantaneous count and said first data componentsto provide said first video components when raster scanning reaches dotpositions designated by said first data components. i

13. The system set forth in claim 11 wherein said timing means alsogenerates horizontal sync pulses, said data signal further includesthird data components associated with respective first data componentsdesignating whether the dot position of its associated first datacomponent is to be displayed in said line being scanned or in asubsequent line, and wherein said first circuit means further comprisesmeans responsive to said horizontal sync pulses and to said third datacomponents to inhibit generation of said first video components whensaid third data components designate beam intensification on asubsequent scan line.

14. The system set forth in claim 9 wherein said data signal furthercomprises third data components each of which designates respective dotpositions along said scan lines and fourth data components each of whichis associated with a respective third data component and designates thedot position of its associated third data component as being the end ofa line segment, said first circuit means is responsive to said thirddata components'to generate output signals when raster scanning reachesdot positions designated by said third data components and wherein saidsecond circuit means comprises means including gate means responsive tosaid output signals and to said fourth data components to inhibit saidbeam at said display when said beam reaches dot positions designated bysaid third data components.

15. The system set forth in claim 9 wherein said second data componentsdesignate that said line segments extend in a direction along said scanlines, and wherein said second circuit means comprises means includinggate means responsive to said first video component signals and saidsecond data components to generate second video components forintensifying said beam at successive dot positions along said scanlines.

16. The system set forth in claim 9 wherein said second data componentsdesignate that said line segments are generally orthogonal to said scanlines, said second circuit means comprises gate means and recirculatingshift register means operated in synchronism with said scanning raster,and wherein said gate means is respon- 1 1 sive to said first videocomponents and second data components associated therewith to causepulses to be entered into said register means when raster scanningreaches dot positions designated by said first data components, saidrecirculating shift register means being arranged to generate saidsecond video components during succeeding scan lines at dot positionstherealong contained in said orthogonal line segments.

17. The method of generating a graphics display on a beam-type displaydevice that exhibits a television raster scan line pattern wherein thebeam traverses successive generally parallel scan lines with a pluralityof display positions along each scan line at which the beam may beintensified to change the display, said display device having a firstpredetermined maximum number of display positions, the steps ofproviding a plurality of storage locations for digital datacorresponding to a second predetermined maximum number of displaypositions at which the intensity of the display may be changed, storingin said storage locations a plurality of digital data words coded toidentify selected display positions at which the intensity of thedisplay is to be changed, successively reading each of said words fromsaid storage locations one by one in synchronism with raster scanning ofa plurality of scan lines while changing the intensity of the display byreading another word in response to said beam reaching that selecteddisplay position identified by that word which was last read and alsochanging the intensity of said display in response to said beam reachingthat selected display position identified by that word which was lastread so that storage locations are required for data corresponding todisplay positions where beam intensity is to be changed rather than fordata at each of said first predetermined maximum number of displaypositions.

18. A system for generating displays on a beam-type display device thatexhibits a television raster scan line pattern wherein each scan lineincludes a plurality of predetermined positions at which the intensityof said beam may be selectively switched between first and second statesof intensification comprising memory storage means for storing aplurality of codes that identify selected display positions in aplurality of scan lines, first means responsive to sequencing signals toread said codes from said memory means one at a time and provide arespective digital signal representing each of said codes, second meansresponsive to a clock pulse signal synchronized with scanning of saidbeam and to each of said digital signals as it is read from memory togenerate a beam control signal each time said beam reaches that displayposition identified by the last code read from said storage means, thirdmeans responsive to each said control signal to generate a beamswitching signal adapted to switch said beam from one intensificationstate to the other intensification state and fourth means responsive toeach said control signal to generate a respective sequencing sig nal forsaid first means to thereby cause another code to be read from memoryidentifying another selected position at which said beam is to beswitched,

19. The method of generating a graphics display on a beam-type displaydevice that exhibits a television raster scan line pattern wherein abeam scans consecutive scan lines each of which includes a plurality ofpredetermined positions at which the intensity of said beam may beselectively switched between first and second states of intensificationto create a display comprising the steps of storing a plurality of datacodes in a main memory with each code identifying a respective selecteddisplay position at which said beam is' to be switched, said storedcodes identifying consecutive positions at which said beam is to beswitched in at least first and second consecutive scan lines, andwherein said method further comprises generating said display bysequentially reading said codes from said memory one at a time toconsecutively identify said selected display positions as said beamscans said consecutive scan lines, said sequential code readingincluding the steps of reading a first data code from memory,identifying a first selected display position in said first linecorresponding to said first data code, generating a first beam controlsignal in response to said beam reaching said first display position,generating a first beam switching signal in response to said firstcontrol signal to switch said beam at said display, reading a seconddata from said memory in response to said first control signal toidentify a second selected display position in said second line,generating a second beam control signal in response to said beamreaching said second display position, generating a second beamswitching signal in response to said second control signal to switchsaid beam at said display, and reading a third data code from saidmemory in response to said second control signal to identify a thirdselected display position at which said beam is to be switched and.wherein each time said beam reaches a selected display positionidentified by that code which was read last, a beam control signal isgenerated to cause another code to be read from said memory.

1. In a system for displaying graphics on a beam-type display device that exhibits a television raster scan line pattern wherein the beam traverses successive generally parallel scan lines with a plurality of predetermined positions along each scan line corresponding to a respective point from which a line may be drawn in a direction generally orthogonal to said scan lines comprising storage means providing digital data coded with a number representing a first predetermined dot position along one of said scan lines and further coded to designate that said line in said generally orthogonal direction is to be drawn from said first dot position, first circuit means responsive to said number code to generate a beam switching control signal when scanning reaches said first dot position in said one scan line and means including a recirculating memory responsive to said beam switching control signal and to said line drawing code for producing a plurality of beam switching signals during scan lines subsequent to said one scan line, said recirculating memory having at least a number of stages corresponding to the number of useable dot positions in any given scan line and being recirculated in synchronism with said scanning raster.
 2. The system set forth in claim 1 further comprising a raster scan timing circuit providing a dot clock pulse train containing a number of pulses equal to said useable number of dot positions in each scan line and wherein said recirculting memory is a recirculating shift register that is shifted in response to said dot clock pulse train.
 3. The method of generating a graphics display on a beam-type display device that exhibits a television raster scan line pattern wherein the beam traverses successive generally parallel scan lines with a plurality of dot positions along each scan line corresponding to respective points at which the beam may be intensified to display a dot, said display device having a first predetermined maximum number of dot positions at which a dot can be displayed, the steps of providing a plurality of storage locations for digital data corresponding to a second predetermined maximum number of dot positions to be intensified in any given display, said second number of dot positions being substantially less than said first number of dot positions, storing in said storage locations a plurality of digital data words coded to identify selected positions at which dots are to be displayed, successively reading each of said words from said storage location one by one in synchronism with raster scanning over a plurality of scan lines while intensifying said beam in response to each word when said beam reaches each predetermined dot position, said words being read successively one by one by reading another code each time said beam reaches that selected dot position identified by that code which was last read, and wherein said data words are coded to designate whether each dot is to be displayed at a dot position specified thereby during the scan line then being traversed by said beam or during the next succeeding scan line to be traversed by said beam, and further comprising the step of inhibiting beam intensification at a dot position in the scan line being traversed in response to a word coded to designate that the dot be displayed at a dot position in the next scan line.
 4. The method of generating a graphics display on a beam-type display device that exhibits a television raster scan line pattern wherein the beam traverses successive generally parallel scan lines with a plurality of dot positions along each scan line corresponding to respective points at which the beam may be intensified to display a dot, said display device having a first predetermined maximum number of dot positions at which a dot can be displayed, the steps of providing a plurality of storage locations for digital data corresponding to a second predetermined maximum number of dot positions to be intensified in any given display, said second number of dot positions being substantially less than said first number of dot positions, storing in said storage locations a plurality of digital data words coded to identify selected positions at which dots are to be displayed, successively reading each of said words from said storage location one by one in synchronism with raster scanning over a plurality of scan lines while intensifying said beam in response to each word when said beam reaches each predetermined dot position, said words being read successively one by one by reading another code each time said beam reaches that selected dot position identified by that code which was last read, and wherein said method further comprises the steps of coding a first word to designate that a line is to be drawn from a starting point dot position designated by said first word, and then, in response to said line drawing code, intensifying said beam at a dot position adjacent said starting point dot position.
 5. The method set forth in claim 4 wherein a horizontal line is to be drawn and said first word is coded to designate that a horizontal line is to be drawn, and wherein said line is drawn by intensifying said beam at said starting point dot position and then, in response to said line drawing code, maintaining said beam intensified as it is scanned across said adjacent dot position.
 6. The method set forth in claim 5 wherein a second word is coded to designate an end point dot position of said horizontal line, and said second word is further coded to designate that drawing of said horizontal line is to be terminated at said end point dot position, and wherein said method further comprises turning off said beam at said end point dot position in response to said further code of said second word.
 7. The method set forth in claim 4 wherein a vertical line is to be drawn and said first word is coded to designate that a vertical line is to be drawn, and wherein said beam is intensified at said adjacent dot position by storing said starting point dot position in a recirculating memory in response to said line drawing code and recalling said stored dot position at the corresponding dot position in the next successive scan line.
 8. The method set forth in claim 7 wherein said recirculating memory is a recirculating shift register, said starting point dot position is stored by entering a pulse in said shift register, and said pulse is recirculated in said shift register in synchronism with beam scanning each time said beam completes one scan line.
 9. A system for displaying graphics including line-like segments on a beam-type display device that exhibits a television raster scan line pattern wherein the beam traverses successive generally parallel scan lines in a first direction and a plurality of predetermined positions along each scan line correspond to points at which the beam may be intensified to display a dot, comprising data storage means providing a digitally coded data signal having first data components each of which designates respective dot positions along said scan lines, said data signal further having second data components associated with respective first data components and designating whether its associated dot position is contained in a line segment, first circuit means operable in synchronism with raster scanning on said display device and responsive to said first data components to generate first video components for intensifying said beam at said designated dot positions and second circuit means operable in synchronism with raster scanning on said display device and responsive to both said first and said second data components to generate second video components for intensifying said beam at other dot positions such that associated first and second data components cause said beam to be intensified at one of said predetermined dot positions on a given line segment and at other dot positions on the same given line segment.
 10. The system set forth in claim 9 wherein said first circuit means generates memory sequencing signals in synchronism with said first video components and wherein said system further comprises means responsive to said memory sequencing signals to sequentially transfer data from said storage means to said first circuit means.
 11. The system set forth in claim 10 further comprising raster scan timing means for generating a dot clock pulse train with each of the pulses therein representing a respective dot position along a scan line and wherein said first circuit means includes counter means and is responsive to said dot clock pulse train and said first data components to generate said first video components when raster scanning reaches said dot positions designated by said first data components.
 12. The system set forth in claim 11 wherein said counter means is responsive to said pulse train to provide an instantaneous count representing the dot position of said beam during each scan line and wherein said first circuit means further comprises comparison means operatively coupled to said storage means and to said counter means and responsive to said instantaneous count and said first data components to provide said first video components when raster scanning reaches dot positions designated by said first data components.
 13. The system set forth in claim 11 wherein said timing means also generates horizontal sync pulses, said data signal further includes third data components associated with respective first data components designating whether the dot position of its associated first data component is to be displayed in said line being scanned or in a subsequent line, and wherein said first circuit means further comprises means responsive to said horizontal sync pulses and to said third data components to inhibit generation of said first video components when said third data components designate beam intensification on a subsequent scan line.
 14. The system set forth in claim 9 wherein said data signal further comprises third data components each of which designates respective dot positions along said scan lines and fourth data components each of which is associated with a respective third data component and designates the dot position of its associated third data component as being the end of a line segment, said first circuit means is responsive to said third data components to generate output signals when raster scanning reaches dot positions designated by said third data components and wherein said second circuit means comprises means including gate means responsive to said output signals and to said fourth data components to inhibit said beam at said display when said beam reaches dot positions designated by said third data components.
 15. The system set forth in claim 9 wherein said second data components designate that said line segments extend in a direction along said scan lines, and wherein said second circuit means comprises means including gate means responsive to said first video component signals and said second data components to generate second video components for intensifying said beam at successive dot positions along said scan lines.
 16. The system set forth in claim 9 wherein said second data components designate that said line segments are generally orthogonal to said scan lines, said second circuit means comprises gate means and recirculating shift register means operated in synchronism with said scanning raster, and wherein said gate means is responsive to said first video components and second data components associated therewith to cause pulses to be entered into said register means when raster scanning reaches dot positions designated by said first data components, said recirculating shift register means being arranged to generate said second video components during succeeding scan lines at dot positions therealong contained in said orthogonal line segments.
 17. The method of generating a graphics display on a beam-type display device that exhibits a television raster scan line pattern wherein the beam traverses successive generally parallel scan lines with a plurality of display positions along each scan line at which the beam may be intensified to change the display, said display device having a first predetermined maximum number of display positions, the steps of providing a plurality of storage locations for digital data corresponding to a second predetermined maximum number of display positions at which the intensity of the display may be changed, storing in said storage locations a plurality of digital data words coded to identify selected display positions at which the intensity of the display is to be changed, successively reading each of said words from said storage locations one by one in synchronism with raster scanning of a plurality of scan lines while changing the intensity of the display by reading another word in response to said beam reaching that selected display position identified by that word which was last read and also changing the intensity of said display in response to said beam reaching that selected display position identified by that word which was last read so that storage locations are required for data corresponding to display positions where beam intensity is to be changed rather than for data at each of said first predetermined maximum number of display positions.
 18. A system for generating displays on a beam-type display device that exhibits a television raster scan line pattern wherein each scan line includes a plurality of predetermined positions at which the intensity of said beam may be selectively switched between first and second states of intensification comprising memory storage means for storing a plurality of codes that identify selected display positions in a plurality of scan lines, first means responsive to sequencing signals to read said codes from said memory means one at a time and provide a respective digital signal representing each of said codes, second means responsive to a clock pulse signal synchronized with scanning of said beam and to each of said digital Signals as it is read from memory to generate a beam control signal each time said beam reaches that display position identified by the last code read from said storage means, third means responsive to each said control signal to generate a beam switching signal adapted to switch said beam from one intensification state to the other intensification state and fourth means responsive to each said control signal to generate a respective sequencing signal for said first means to thereby cause another code to be read from memory identifying another selected position at which said beam is to be switched.
 19. The method of generating a graphics display on a beam-type display device that exhibits a television raster scan line pattern wherein a beam scans consecutive scan lines each of which includes a plurality of predetermined positions at which the intensity of said beam may be selectively switched between first and second states of intensification to create a display comprising the steps of storing a plurality of data codes in a main memory with each code identifying a respective selected display position at which said beam is to be switched, said stored codes identifying consecutive positions at which said beam is to be switched in at least first and second consecutive scan lines, and wherein said method further comprises generating said display by sequentially reading said codes from said memory one at a time to consecutively identify said selected display positions as said beam scans said consecutive scan lines, said sequential code reading including the steps of reading a first data code from memory, identifying a first selected display position in said first line corresponding to said first data code, generating a first beam control signal in response to said beam reaching said first display position, generating a first beam switching signal in response to said first control signal to switch said beam at said display, reading a second data from said memory in response to said first control signal to identify a second selected display position in said second line, generating a second beam control signal in response to said beam reaching said second display position, generating a second beam switching signal in response to said second control signal to switch said beam at said display, and reading a third data code from said memory in response to said second control signal to identify a third selected display position at which said beam is to be switched and wherein each time said beam reaches a selected display position identified by that code which was read last, a beam control signal is generated to cause another code to be read from said memory. 